EARTH AND ITS

RESOURCESForces that Shape the Earth

Chapter 5, lesson 4

WHAT IS WEATHERING? Weathering: the breaking down of rock

into smaller pieces by natural process IceMoving WaterVegetation

TWO TYPES OF WEATHERING

1. PHYSICAL Breaking down of rock

by physical movements Water Plants Animals

Frost wedges into cracks and expands

Moving water carries pieces of rock

Plants root under rocks and grow

Animals burrow and bring pieces underground

TWO TYPES OF WEATHERING(CONT.)2. CHEMICAL

Breaking down of rock by changes in its chemical composition Oxygen VS iron Acids

Rocks contain iron which reacts with oxygen in the air

Oxygen and iron make rust, which makes the rock less strong than it was before

Carbonic acid, or acid rain, can wear away at natural limestone

EROSION AND DEPOSITION

Erosion is the picking up and removing of rock pieces

Deposition is the dropping off of particles in another location

Wind contributes to erosion Carries small particles in the

wind Shapes sand dunes

Water contributes to erosion Freezing and thawing changes

landscape Melting snow affects soft rocks

EROSION AND DEPOSITION (CONT.)

Flowing water is a major cause of erosion

When the river slows down, some of the particles are deposited as sediment, or loose pieces of rock

This can cause the river to meander, or curve

HOW CAN MOVING WATER CHANGE THE LAND?

Gravity and glaciers are other agents that cause erosion

Glaciers form when more snow falls than it can melt When ice sheets are about 100 meters thick, it

begins to fall downhill When it falls, it takes loose pieces of land with it This mixture of land pulled loose by glaciers is called till These deposits take the form of a ridge or mound, called

a moraine

HOW IS SOIL FORMED? Weathering results in loose rock

pieces which become a part of soil

Soil: a mixture of weathered rock, air, water, living things, and humus Humus: material made of decayed

plant and animal remains Bacteria, fungi, worms, and insects

all contribute to the formation

When plants or animals die, their remains enrich the soil and develop layers called soil horizons

WHY IS SOIL IMPORTANT? Minerals in soil cannot be replaced, it must be

conserved Soil can be ruined by…..

Growing too many plantsOr the same plants many years in a row

Dumping waste in soilPaving over landBuilding dams